From German Pat. No. 23 21 070, for example, it is known to provide an apparatus for the electric arc welding of two workpieces of fusible metal, preferably pipe ends, rings or the like, along a closed weld path, for example a circular, elliptical, polygonal or other annular weld seam, with the aid of at least two unipolar magnets lying in the welding plane and disposed generally radially to magnetize a continuous ring encircling the weld-seam path. The distribution of the magnets and their connection is such as to homogenize the magnetic field and the ring can be radially separable.
The electric arc welding of annular bodies along an endless weld seam in the aforementioned manner is effected by bringing together the two workpieces so that their junction lies in the plane of the magnets and an arc can be struck between the workpieces which are connected to an appropriate electric current source, the welding arc migrating under the influence of the magnetic field around the weld-seam path to form the endless weld seam.
While the system described in this publication is highly effective and represents a substantial improvement over earlier arrangements because of its lower structural height and relatively high magnetic field concentration at the weld site, the maximum field strength which can be generated is nevertheless limited.